fix

Author: Caideyipi

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/sink/protocol/opcua/OpcUaSink.java

@@ -307,8 +307,8 @@ private void customizeClient(final String nodeUrl, final PipeParameters paramete
         policy = SecurityPolicy.Aes256_Sha256_RsaPss;
         break;
       default:
-        policy = null;
-        break;
+        throw new PipeException(
+            "The security policy can only be 'None', 'Basic128Rsa15', 'Basic256', 'Basic256Sha256', 'Aes128_Sha256_RsaOaep' or 'Aes256_Sha256_RsaPss'.");
     }
 
     final IdentityProvider provider;